JP2009105884A - Receiver for spread spectrum radar - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiver for spread spectrum radar that obtains an accurate radar spectrum. <P>SOLUTION: The receiver for spread spectrum radar for receiving spread spectrum signals includes a despreading portion 114 for outputting a first despread signal and second despread signal passing through a transmission line carrying a current having a current value identical to a current value of a current carried by a transmission line through which the first despread signal passes, and an orthogonal demodulation portion 116 for outputting an in-phase signal and orthogonal signal by orthogonally demodulating the first and second despread signals. The despreading portion 114 includes a first and second transistors having the identical characteristics. The received signals are despread by turning the first and second transistors on or off in response to a pseudo noise code. Then, the first despread signal is outputted by the first transistor, and the second despread signal by the second transistor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a spread spectrum radar receiver mounted on a radar device using a spread spectrum system, and in particular, spread spectrum capable of obtaining an accurate radar spectrum whose intensity is stable without depending on the phase of a received signal. The present invention relates to a receiving device for a type radar device.

  In recent years, radar devices are mounted on automobiles and are also used for detecting preceding vehicles and obstacles behind them. As a result, significant results such as improvement of safety such as collision avoidance and improvement of driving convenience represented by backward departure support are expected. Accordingly, technological development relating to radar devices (hereinafter referred to as in-vehicle radar devices) mounted on automobiles has been activated. In the in-vehicle radar device, it is very important to suppress the influence of radio waves transmitted from the same type of radar device mounted on another vehicle. As an example, a radar apparatus using a spread spectrum system (hereinafter referred to as a spread spectrum radar apparatus) has been proposed.

  In a spread spectrum radar apparatus, a transmission radio wave is modulated by a pseudo noise code (hereinafter referred to as a PN (Pseudo Noise) code) used for spreading. The receiver despreads the reflected wave reflected from the object by the same code as the PN code used when modulating the transmission radio wave. For this reason, radio waves modulated with different codes or radio waves radiated from other types of radar devices without code modulation are suppressed in the receiver. Further, since the transmission radio wave is frequency-spread by the PN code, the power per unit frequency can be reduced and the influence on other radio systems can be reduced. Further, the relationship between the distance resolution and the maximum detection distance can be freely set by adjusting the chip rate and code cycle of the PN code. Further, since radio waves can be transmitted continuously, peak power does not increase.

  FIG. 1 is a diagram illustrating a configuration of a receiving unit of a conventional spread spectrum radar receiver. The receiving unit 300 in the figure includes a receiving antenna 301, a low noise amplifier 302, a despreading unit 303, a phase shifter 304, a quadrature demodulating unit 305, and buffer amplifiers 307a and 307b.

  A transmission signal transmitted by being spread over an ultra-wide band by the transmission device is reflected by an object at a certain distance. The reflected signal reflected by the object is received by the receiving antenna 301 of the receiving unit 300 in FIG. The reflected signal is despread using the PN code input from the receiving PN code generation unit 310 to the despreading unit 303 and converted into a narrowband signal. Thereafter, the narrowband signal is propagated by being divided into differential lines having different phases by 180 °. The two narrowband signals are down-converted by the balanced modulators 305a and 305b based on two local oscillation signals generated by the local oscillator 306 and the phase shifter 304 and having a phase difference of about 90 °, An orthogonal signal is output. The intensity of the signal can be calculated by calculating the sum of squares of the in-phase signal and the quadrature signal. Further, a control unit (not shown) in the receiving apparatus controls how much delay time the receiving unit 300 uses the same PN code as the PN code used in the transmitting apparatus. Then, the signal processing unit 320 performs signal processing on the signal obtained by the receiving unit 300, thereby calculating the distance of the object and reflecting it in the radar spectrum.

  FIG. 2 is a diagram illustrating a circuit configuration of the despreading unit 303 and the balanced modulators 305a and 305b included in the quadrature demodulation unit 305 of the receiving apparatus disclosed in Patent Document 1. Each of the despreading unit 303 and the balanced modulators 305a and 305b is a switch circuit having a double balance input / output configuration, and all the transistors in the amplification stage of the Gilbert cell mixer are omitted. By configuring a circuit in which the despreading unit 303 and the balanced modulators 305a and 305b are integrated as shown in the figure, the current power supply circuit 331 can be shared. As a result, the current value consumed can be reduced, and low power consumption can be realized. In addition, since the received signal output from the collector of the transistor included in the despreading unit 303 can be input directly to the emitter of the transistor included in the balanced modulators 305a and 305b, the influence of distortion can be suppressed. Furthermore, the chip size can be reduced.

  FIG. 3 is a simplified diagram showing the operation of the receiving unit 300 shown in FIG. The received signal is converted from an unbalanced signal to a balanced signal by the balun 330. As shown in FIG. 3, currents flowing through the balanced output lines of the balun 330 are A and B, respectively. In addition, it is assumed that the transistors Q1, Q7, Q9, Q12, Q13, and Q16 are on, and the other transistors are off.

  A current A flows through the transistor Q1, and a current B flows through the transistor Q7. In the quadrature demodulating unit 305, the transistors Q9, Q12, Q13, and Q16 are in the on state, so the current A is constituted by the current A1 that flows through the transistor Q9 and the current A2 that flows through the transistor Q13. The current B is constituted by a current B1 flowing through the transistor Q12 and a current B2 flowing through the transistor Q16. Here, if the currents A1 and A2 and the currents B1 and B2 are equal, the output signal strengths of OUT1 and OUT3 and the output signal strengths of OUT2 and OUT4 are also equal. That is, it can be said that the in-phase balanced signal composed of OUT1 and OUT2 is equal to the quadrature balanced signal composed of OUT3 and OUT4. Hereinafter, a process for obtaining a radar spectrum more specifically using mathematical expressions will be described.

  The two balanced signals RF1 and RF2 that have passed through the despreading unit 303 are (Equation 1), and the two local oscillation signals LO_I and LO_Q that are input to the quadrature demodulation unit 305 with different 90 ° phases are represented by (Equation 2). The

(Equation 1)
RF1 = P ₁ cos (ω ₁ t + φ)
RF2 = P ₂ cos (ω ₁ t + φ + π)
(Equation 2)
LO_I = cos ω ₂ t
LO_Q = sinω ₂ t

P ₁ and P ₂ indicate the balanced signal strength, and φ indicates the phase of the received signal. The reception signal RF is modulated by the quadrature demodulation unit 305 based on the local oscillation signals LO_I and LO_Q. An output in-phase signal obtained by removing a signal having a high frequency from the modulated signal with a filter is represented by IF_I, and an output quadrature signal by IF_Q is represented by (Equation 3).

(Equation 3)
_{IF_I = (P 1/2)} cos {(ω 1 -ω 2) t + φ}
_{IF_Q = (P 2/2)} sin {(ω 1 -ω 2) t + φ}

  The sum of squares T of the in-phase signal IF_I and the quadrature signal IF_Q is expressed by (Expression 4).

(Equation 4)
_{T = √ [(P 1/} 2) 2 cos 2 {(ω 1 -ω 2) t + φ} + (P 2/2) 2 sin 2 {(ω 1 -ω 2) t + φ}]

The square sum T of the in-phase signal and the quadrature signal is reflected as a peak of the radar spectrum. At this time, if the values of the signal strengths P ₁ and P ₂ of the two balanced signals RF1 and RF2 after passing through the despreading unit 303 are different, the sum of squares T of the in-phase signal and the quadrature signal depends on the phase φ of the received signal. Change. However, if the values of the signal strengths P ₁ and P ₂ are equal, it can be seen that the sum of squares T of the in-phase signal and the quadrature signal is always a constant value.

The values of the signal strengths P ₁ and P ₂ of the two balanced signals RF1 and RF2 after passing through the despreading unit 303 are the difference between the current values A1 and B1 or the difference between the current values A2 and B2 in FIG. Dependent. If the absolute value of the difference between the two current values is equal, the square sum T of the in-phase signal and the quadrature signal is always a constant value from the result of (Equation 4), and the peak intensity of the received signal can be stabilized. it can.
JP 2005-72735 A

  However, the receiving apparatus according to the conventional technique has a problem that the values of the in-phase balanced signal and the quadrature balanced signal are not stable, and the peak of the received signal corresponding to the target at a certain distance is not stable. That is, since the sum of squares of the in-phase balanced signal and the quadrature balanced signal varies depending on the phase φ of the received signal, the peak of the received signal corresponding to the target at a certain distance is not stable, and the intensity varies.

  More specifically, the bases of the transistors Q9 and Q13 are not common in the conventional circuit configuration. For this reason, when a difference occurs in the DC voltage levels of the local oscillation signals LO1 and LO3 due to the effect of the matching circuit with the previous stage circuit, a difference also occurs in the base input voltages of Q9 and Q13. When the transistor element is in the on state, the base-emitter voltage is kept constant (the voltage value varies depending on the material and process of the transistor).

  However, when the base-emitter voltage changes, the collector current changes exponentially depending on the base-emitter voltage. As a result, assuming that the DC voltage level of the local oscillation signal LO1 increases and the DC voltage level of the local oscillation signal LO3 decreases, the emitters of the transistors Q9 and Q13 are common. It becomes higher than the base-emitter voltage of Q13. Therefore, it is considered that almost all of the current A flows through the transistor Q9 and almost no current flows through the transistor Q13. In the same way, it is considered that almost all of the current B flows through the transistor Q12 and almost no current flows through the transistor Q16.

As described above, when A1 ≠ A2 or B1 ≠ B2, the values of the signal strengths P ₁ and P ₂ are different. In this case, since the sum of squares T shown in (Equation 4) changes depending on the phase φ of the received signal, the peak of the received signal is not stable and the intensity varies. That is, when the voltage level of the signal input to the base of each transistor fluctuates due to the influence of noise or the like, the output signal intensity is different, and an accurate radar spectrum cannot be obtained.

  Therefore, the present invention has been made in view of the above problems, and by maintaining the sum of squares of the in-phase signal and the quadrature signal constant without depending on the phase of the received signal, the signal strength is stabilized, and the accurate An object of the present invention is to provide a spread spectrum radar receiver capable of obtaining a radar spectrum.

  In order to solve the above problems, a spread spectrum radar receiver of the present invention is a spread spectrum radar receiver that receives a spread spectrum spread signal, and receives the spread signal as a received signal. And a current value that is the same as the current value of the first despread signal and the line on which the first despread signal propagates by despreading the received signal input to the signal receiving unit using a pseudo-noise code A despreading unit that outputs a second despread signal propagating through a line through which current flows, and quadrature demodulating the first despread signal and the second despread signal, thereby obtaining an in-phase signal and a quadrature signal, The despreading unit includes a first transistor pair including a first transistor and a second transistor having the same characteristics, and the first transistor and the second transistor. The reception signal is input, and the reception signal is despread by turning on or off according to the pseudo-noise code, the first transistor outputs the first despread signal, and the second transistor Outputs the second despread signal, and the quadrature demodulator demodulates the first despread signal using a first local oscillation signal and outputs the in-phase signal; And a second demodulator that demodulates the second despread signal using a second local oscillation signal whose phase is shifted by 90 degrees and outputs the orthogonal signal.

  Thereby, the current value of the in-phase signal and the current value of the quadrature signal can be kept constant by keeping the current values of the lines through which the two despread received signals output from the despreading unit propagate. it can. Therefore, the square sum of the in-phase signal and the quadrature signal can be kept constant, and an accurate radar spectrum can be obtained.

  The signal receiving unit converts the received spread signal into a balanced received signal composed of a positive received signal and a negative received signal, and the first despread signal is a first positive despread signal and a first negative despread signal. The second despread signal is a balanced signal composed of a second positive despread signal and a second negative despread signal, and the despreading unit further includes the first transistor pair. The first transistor pair receives the positive received signal, and despreads the positive received signal by turning on or off according to the pseudo-noise code, 1 forward despread signal and 2nd forward despread signal are output, and the negative received signal is input to the second transistor pair by turning on or off according to the pseudo noise code. Despreading the first negative inverse Wherein the diffuser signal second negative despread signal and may output.

  More preferably, the pseudo-noise code is a balanced pseudo-noise code composed of a positive pseudo-noise code and a negative pseudo-noise code, and the despreading unit further includes a third transistor pair having the same configuration as the first transistor pair. And the fourth transistor pair, and the first transistor pair despreads the normal reception signal by turning on or off according to the positive pseudo-noise code, and the first normal / despread signal and the second transistor The second transistor pair despreads the negative reception signal by turning on or off according to the positive pseudo-noise code, and outputs the first negative despread signal and the second despread signal. A negative despread signal, and the third transistor pair receives the positive received signal and de-spreads the positive received signal by turning on or off according to the negative pseudo-noise code. Negative The fourth transistor pair receives the negative received signal and turns on or off according to the negative pseudo-noise code to reverse the negative received signal. Spreading and outputting the first forward and reverse spread signal and the second forward and reverse spread signal.

  As a result, the received signal can be processed as a balanced signal, and the influence of external noise can be reduced.

  The spread spectrum radar receiver may further include a code generation unit that generates the pseudo noise code, and an amplification circuit that amplifies the pseudo noise code and outputs the amplified pseudo noise code to the despreading unit.

  Thus, by amplifying the output intensity of the PN code, the transistor included in the despreading unit can be operated in the saturation region, and a stable received signal intensity can be obtained. Furthermore, it is not necessary to provide a large capacitor for removing DC voltage outside the chip.

  The signal receiving unit may include a balun circuit that converts the received spread signal into the balanced received signal and outputs the balanced received signal to the despread unit, and the balun circuit may be configured with a passive element.

  As a specific configuration, the balun circuit is electromagnetically connected to the first transmission line, the first transmission line having one end to which the spread signal that is an unbalanced signal is input and the other end is grounded. A second transmission line and a third transmission line, wherein one end of the second transmission line and one end of the third transmission line are grounded, and the other end of the second transmission line facing each other and the third transmission line The positive reception signal and the negative reception signal are respectively output from the other end of the transmission line.

  Thereby, compared with the case where the balun is composed of an active element such as a transistor, the distortion of the received signal output as the balanced signal can be reduced.

  The spread spectrum radar receiver further includes a first capacitor connected in parallel to the output line of the first demodulator to remove a high frequency component of the in-phase signal, and an output of the second demodulator. And a second capacitor connected in parallel to the line and removing a high-frequency component of the orthogonal signal.

  Thereby, the high frequency component of the despread signal which has propagated through the receiving device without being despread by the despreading unit can be removed. It is possible to suppress the despread signal from being distorted by the high frequency component, and to prevent the peak of the modulation signal due to the distortion from appearing in the radar spectrum.

  The despreading unit and the quadrature demodulation unit may be an integrated circuit having a common current source, and may be formed on the same semiconductor substrate.

  As a result, a current power supply circuit that supplies current to the despreading unit and the orthogonal demodulation unit can be made common, power consumption can be suppressed, and the chip size can be reduced.

  The transistor may be a heterobipolar transistor.

  As a result, it can be used as a radar apparatus capable of higher frequency operation.

  According to the present invention, the sum of the squares of the in-phase signal and the quadrature signal output from the quadrature demodulation unit is made constant regardless of the phase of the received signal, thereby stabilizing the strength of the received signal and obtaining an accurate radar spectrum. It is possible to provide a spread spectrum radar receiving apparatus capable of performing the above.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
In the spread spectrum radar receiver of this embodiment, the despreading unit and the quadrature demodulation unit have a double-balanced input / output switch circuit configuration, a common current power supply circuit, and a common despreading unit with emitter and base 4 pairs of transistors. The current values output from the transistors included in each transistor pair are configured to have the same value.

  FIG. 4 is a configuration diagram of the spread spectrum radar receiver of the present embodiment. The spread spectrum radar receiver 100 in the figure receives the detection radio wave transmitted from the spread spectrum radar transmitter 150 and reflected by the object. Then, by processing the received radio waves for detection, the distance to the object and the relative speed are detected. The spread spectrum radar receiving apparatus 100 includes a receiving unit 110, a receiving PN code generating unit 120, a signal processing unit 130, and a control unit 140.

  The receiving unit 110 receives a detection radio wave reflected from an object among the detection radio waves transmitted from the spread spectrum radar transmitter 150, and performs a despreading process and an orthogonal demodulation process. Details of the configuration of the receiving unit 110 will be described later.

  Based on the timing signal supplied from the control unit 140, the reception PN code generation unit 120 generates a PN code generated by a transmission PN code generation unit (not shown) in the spread spectrum radar transmitter 150. A time-delayed PN code is generated, and the generated PN code is supplied to the receiving unit 110.

  The signal processing unit 130 supplies the code delay time τ of the reception PN code generated by the reception PN code generation unit 120 with respect to the transmission PN code generated by the transmission PN code generation unit, supplied from the spread spectrum radar transmission device 150 The presence / absence of an obstacle, the distance, the relative speed, and the like are calculated based on the reference signal to be output and the signal output from the receiving unit 110.

  The control unit 140 supplies a timing signal to the reception PN code generation unit 120 and the transmission PN code generation unit.

  FIG. 5 is a diagram illustrating a configuration of the receiving unit 110 of the spread spectrum radar receiving apparatus according to the present embodiment. The receiving unit 110 in the figure includes a receiving antenna 111, a low noise amplifier 112, a balun 113, a despreading unit 114, a phase shifter 115, a quadrature demodulation unit 116, capacitors 118a and 118b, and buffer amplifiers 119a and 119b. Note that the signal receiving unit described in the claims corresponds to the receiving antenna 111, the low noise amplifier 112, and the balun 113.

  The reception antenna 111 is an antenna that receives a detection radio wave reflected by an object as a reception signal. In the present embodiment, for example, the detection radio wave is spread in a frequency band of 26.4 GHz ± 1 MHz.

  The low noise amplifier 112 is inserted as necessary in order to keep a good signal-to-noise ratio. The circuit is composed of single wiring.

  The balun 113 is a circuit that converts a received signal input as an unbalanced signal into a balanced signal. FIG. 6 is a diagram illustrating a circuit configuration of the balun 113. The balun 113 includes four transmission lines 161, 162, 163 and 164, and a capacitor 165. As shown in the figure, it is possible to prevent the received signal from being distorted by configuring the balun only with passive elements.

  A transmission signal is input to one end of the transmission line 161. The other end of the transmission line 161 is connected to one end of the transmission line 162. The other end of the transmission line 162 is grounded. One ends of the transmission line 163 and the transmission line 164 are grounded. The other ends of the transmission line 163 and the transmission line 164 are connected to the despreading unit 114. The transmission lines 161 and 163 and the transmission lines 162 and 164 are electromagnetically connected to each other, and a reception signal input as an unbalanced signal to the transmission line 161 is received as a balanced signal from the other ends of the transmission lines 163 and 164. It is output to the despreading unit 114. The capacitor 165 is connected in parallel to the transmission lines 163 and 164 in order to match the balun and the circuit connected thereto.

  The despreading unit 114 modulates the received signal converted into the balanced signal by the balun 113 based on the PN code. At this time, if the code delay time τ of the reception PN code with respect to the transmission PN code is equal to the delay time corresponding to the distance to the detection target, the PN code included in the received detection radio wave and the reception PN The signal that is in phase with the PN code supplied from the code generator 120 and is spread in a wide band is despread and restored. When the delay time is different from the delay time corresponding to the distance to the detection target, the modulation signal output from the despreading unit 114 remains spread over a wide band.

  The phase shifter 115 generates a local oscillation signal that is approximately 90 ° out of phase with the local oscillation signal generated by the local oscillator 117. In addition, about 90 degrees is a range from 85 degrees to 95 degrees.

  The frequency of the local oscillation signal generated by the local oscillator 117 is 20 to 30 GHz (for example, 26 GHz band), or 30 GHz to 100 GHz (for example, 60 GHz band or 76 GHz band).

  The quadrature demodulator 116 includes balanced modulators 116a and 116b. The quadrature demodulation unit 116 uses the local oscillation signal, and converts the modulated signal output from the despreading unit 114, that is, the signal subjected to the despreading process, into an in-phase signal and a quadrature signal of an intermediate frequency.

  Capacitors 118a and 118b are connected in parallel to a balanced line between balanced modulators 116a and 116b and buffer amplifiers 119a and 119b. By connecting the capacitor to this position, it is possible to remove the high-frequency component of the spread signal that has propagated through the receiving device without being despread by the despreading unit 114. Since the spread signal is composed of many frequency components, it is a signal having a large amplitude when viewed from the time axis spectrum. In particular, in the case of a reflected signal from a strong reflector, the amplitude of this diffused signal is further increased. Distortion occurs when this amplitude is greater than the 1 dB gain compression point of the circuit in the receiver. When distortion occurs, the spread signal is modulated, and in the distance detection spectrum, the modulated signal may appear as a peak at a distance where no object actually exists.

  The buffer amplifiers 119a and 119b amplify the signal strength of the in-phase signal and the quadrature signal having the intermediate frequency output from the quadrature demodulation unit 116. Here, the amplified signal is input to the signal processing unit 130, and the received signal intensity is reflected in the radar spectrum.

  FIG. 7 is a diagram showing circuit configurations of the despreading unit 114 and the balanced modulators 116a and 116b constituting the quadrature demodulation unit 116 in FIG. Each of the despreading unit 114 and the balanced modulators 116a and 116b is a switch circuit having a double-balanced input / output configuration, and has a circuit configuration in which all the transistors in the amplification stage of the Gilbert cell mixer are omitted.

  The circuit shown in the figure includes 16 transistors Q1 to Q16, four resistors R1 to R4, and a DC power supply Vc. The despreading unit 114 is composed of eight transistors each having a pair of transistors Q1 and Q2, Q3 and Q4, Q5 and Q6, and Q7 and Q8. The balanced modulator 116a includes four transistors Q9, Q10, Q11, and Q12. The balanced modulator 116b includes four transistors Q13, Q14, Q15, and Q16.

  The emitter terminals of the transistors Q1, Q2, Q3, and Q4 are connected to one of the balanced output lines of the balun 113. The emitter terminals of the transistors Q5, Q6, Q7, and Q8 are connected to the other of the balanced output lines of the balun 113. The base terminals of the transistors Q1, Q2, Q7 and Q8 are connected to the PN1 terminal. The base terminals of the transistors Q3, Q4, Q5 and Q6 are connected to the PN2 terminal. The collector terminals of the transistors Q1 and Q5 are connected to the emitter terminals of the transistors Q13 and Q14. The collector terminals of transistors Q2 and Q6 are connected to the emitter terminals of transistors Q9 and Q10. The collector terminals of the transistors Q3 and Q7 are connected to the emitter terminals of the transistors Q15 and Q16. The collector terminals of transistors Q4 and Q8 are connected to the emitter terminals of transistors Q11 and Q12.

  The base terminals of the transistors Q9 and Q12 are connected to the LO1 terminal. The base terminals of the transistors Q10 and Q11 are connected to the LO2 terminal. The base terminals of the transistors Q13 and Q16 are connected to the LO3 terminal. The base terminals of the transistors Q14 and Q15 are connected to the LO4 terminal. The collector terminals of the transistors Q9 and Q11 are connected to one end of the resistor R1 and the OUT1 terminal. The collector terminals of the transistors Q10 and Q12 are connected to one end of the resistor R2 and the OUT2 terminal. The collector terminals of the transistors Q13 and Q15 are connected to one end of the resistor R3 and the OUT3 terminal. The collector terminals of the transistors Q14 and Q16 are connected to one end of the resistor R4 and the OUT4 terminal.

  The other ends of the resistors R1, R2, R3, and R4 are connected to the DC power source Vc. The single input line of the balun 113 and the RF terminal are connected. The resistors R1 to R4 are all resistors having the same resistance value.

  The PN code generated as a balanced signal by the receiving PN code generation unit 120 is input to the PN1 terminal and the PN2 terminal, respectively. Therefore, signals that are 180 degrees out of phase are always input to the PN1 terminal and the PN2 terminal. Thereby, for example, the transistor pair composed of the transistors Q1 and Q2 and the transistor pair composed of the transistors Q3 and Q4 are not substantially turned on at the same time.

  A local oscillation signal LO_I that is a signal output from the local oscillator 117 and in phase with the received signal is input to the LO1 terminal and the LO2 terminal as a balanced signal. A local oscillation signal LO_Q that is output from the phase shifter 115 and has a phase difference of about 90 ° and orthogonal to the received signal is input to the LO3 terminal and the LO4 terminal as a balanced signal.

  The in-phase signal I is output from the OUT1 terminal and the OUT2 terminal. An orthogonal signal Q is output from the OUT3 terminal and the OUT4 terminal.

  A reception signal received by the reception antenna 111 and amplified by the low noise amplifier 112 is input to the RF terminal.

  A current power supply circuit 201 is connected to the balun 113. As described above, by configuring the despreading unit 114 and the quadrature demodulation unit 116 to be integrated, the current power supply circuit 201 supplies current to the balun 113, the despreading unit 114, and the quadrature demodulation unit 116 described above. can do. As a result, current consumption can be significantly reduced, and the chip size can be reduced. Further, since the reception signal (including the modulated reception signal) is not input to the base terminal of the transistor, distortion of the reception signal can be suppressed.

  FIG. 8 is a simplified diagram showing the operations of the despreading unit 114 and the orthogonal demodulation unit 116 shown in FIG.

  As in the conventional configuration, the received signal is unbalanced-balanced converted by the balun 113. As shown in FIG. 8, the currents flowing through the balanced output lines of the balun 113 are A and B, respectively. In addition, it is assumed that the transistors Q1, Q2, Q7, Q8, Q9, Q12, Q13, and Q16 are on, and the other transistors are off.

  Transistors Q1 and Q2 have a common emitter and base. That is, the base-emitter voltages of the transistors Q1 and Q2 are equal. Since the collector current flowing through the transistor is determined by the voltage between the base and the emitter, the collector current flowing through the transistors Q1 and Q2 is also equal. As a result, current A / 2 flows through transistors Q1 and Q2. Transistors Q7 and Q8 have a common emitter and base, respectively. Therefore, current B / 2 flows through transistors Q7 and Q8.

  In the quadrature demodulator 116, the transistor Q9 is in the on state, and the emitter of the transistor Q9 is connected to the collector of the transistor Q2, so that a current A / 2 flows through the transistor Q9. Similarly, a current B / 2 flows through the transistor Q12, a current A / 2 flows through the transistor Q13, and a current B / 2 flows through the transistor Q16.

As described above, by inserting a transistor having a common emitter and base, the current flowing through the output terminals OUT1 and OUT3 and the output terminal OUT2 regardless of changes in the DC voltage level of the local oscillation signal of the quadrature demodulator 116. And OUT4 can be made equal. Thereby, the strength of the in-phase balanced signal at the output terminals OUT1 and OUT2 is always equal to the strength of the quadrature balanced signal at the output terminals OUT3 and OUT4. That is, in (Equation 4), P ₁ and P ₂ are equal, and the square sum T is constant regardless of the phase φ of the received signal. Therefore, the intensity of the received signal is stabilized and an accurate radar spectrum can be obtained.

  As described above, in the spread spectrum radar receiver according to the present embodiment, the sum of the current flowing through the balanced modulator 116a that outputs the in-phase signal and the sum of the current flowing through the balanced modulator 116b that outputs the quadrature signal. Therefore, the despreading unit 114 of the present embodiment is configured by adding a new transistor having a common base and emitter to each of the transistors constituting the conventional despreading unit 303. To do. That is, the despreading unit 114 forms a transistor pair from two transistors having a common base and emitter, and includes four transistor pairs.

  Thereby, the peak intensity of the received signal is stabilized, and an accurate radar spectrum can be obtained. In addition, as before, the despreading unit and quadrature demodulation unit have a switch circuit configuration with a double-balanced input / output configuration, and the current power supply circuit is shared, thereby reducing chip size and power consumption. ing.

(Embodiment 2)
The spread spectrum radar receiver of this embodiment amplifies the signal strength of the PN code input to the despreading unit by inserting a differential amplifier between the receiving PN code generating unit and the despreading unit. To do.

  FIG. 9 is a configuration diagram of the spread spectrum radar receiver according to the present embodiment. The spread spectrum radar receiver shown in the figure is different from the receiver shown in FIG. 5 in that a differential amplifier 210 is further added. In the following, description of the same points as in the receiving apparatus of FIG. In addition, about the component of the receiver shown in FIG. 9, the same code | symbol is attached | subjected about the component same as the structure of FIG.

  In the receiving unit 110a of FIG. 9, a differential amplifier 210 is added between the receiving PN code generation unit 120 and the despreading unit 114 in addition to the configuration of the receiving unit 110 of FIG.

  FIG. 10 is a diagram illustrating a circuit configuration of the differential amplifier 210. The differential amplifier 210 includes transistors Q21, Q22, Q23 and Q24, resistors R5 and R6, a DC power supply Vc, and a current power supply circuit 211.

  The base terminal of the transistor Q21 is connected to the PNin1 terminal. The collector terminal is connected to the base terminal of the transistor Q23 and one end of the resistor R5. The emitter terminal is connected to the emitter terminal of the transistor Q22 and to the current power supply circuit 211. The base terminal of the transistor Q22 is connected to the PNin2 terminal. The collector terminal is connected to the base terminal of the transistor Q24 and one end of the resistor R6. The collector terminal of the transistor Q23 is connected to the collector terminal of the transistor Q24, the other ends of the resistors R5 and R6, and the DC power source Vc. The emitter terminal is connected to the PNout1 terminal and the current power supply circuit 211. The emitter terminal of the transistor Q24 is connected to the PNout2 terminal and the current power supply circuit 211. The other end of the DC power supply Vc is grounded.

  Thus, the balanced signal of the PN code input from the PNin1 terminal and the PNin2 terminal is amplified by the circuit of FIG. 10 and output from the PNout1 terminal and the PNout2 terminal. The despreading unit 114 is a non-linear circuit. When the signal strength of the local signal (here, PN code) is small, the gain of the nonlinear circuit increases in proportion to the local signal strength. On the other hand, when the signal strength of the local signal becomes larger than a certain threshold value, the gain of the nonlinear circuit is saturated and has a saturation characteristic that becomes constant. During radar operation, it is necessary to keep the gain constant even if there is some variation in local signal strength. For this reason, it is necessary to set the local signal strength to operate the nonlinear circuit in the saturation region. By inserting the differential amplifier 210 between the receiving PN code generation unit 120 and the PN code input unit of the despreading unit 114, the local signal strength is set so that the despreading unit 114 can operate in the saturation region. be able to.

  Further, in the spread spectrum radar receiver configuration of FIG. 5, if the output DC voltage level of the receiving PN code generator 120 is not suitable for the input DC voltage levels of the PN1 terminal and PN2 terminal of FIG. It is necessary to connect a large capacitor for removing DC voltage between the code generator 120 and the despreading unit 114. However, by inserting the differential amplifier 210, the output DC voltage level of the receiving PN code generator 120 is not related to the input DC voltage levels of the PN1 terminal and PN2 terminal of FIG. The input DC voltage levels at the PN1 terminal and PN2 terminal in FIG. 7 coincide with the output DC voltage levels at the PNout1 terminal and PNout2 terminal in FIG. The input DC voltage levels at the PNout1 and PNout2 terminals depend on parameters such as the DC voltage source Vc, the voltage drop across the resistors R5 and R6, and the base-emitter voltage values of the transistors Q23 and Q24. As a result, the DC voltage level of the local signal input unit of the despreading unit can be set without being concerned with the output DC voltage level of the receiving PN code generation unit only by the circuit configuration of the differential amplifier in the chip. Does not require a large capacitor for voltage removal.

  As described above, according to the spread spectrum radar receiver of the present embodiment, differential amplifier 210 is inserted between reception PN code generation section 120 and local signal input section of despreading section 114. Thus, the local signal strength can be amplified. Accordingly, the despreading unit 114 having a nonlinear circuit configuration can be operated in the saturation region. Furthermore, a circuit configuration in which an external capacitor having a large size for removing DC voltage is not required can be obtained.

  The spread spectrum radar receiver of the present invention has been described based on the embodiment. However, the present invention is not limited to this embodiment. Unless it deviates from the meaning of this invention, the form which carried out the various deformation | transformation which those skilled in the art can think to this embodiment, and the structure constructed | assembled combining the component in different embodiment is also contained in the scope of the present invention. .

  For example, although a bipolar transistor is used as the transistor in the above description, a heterobipolar transistor may be used. A field effect transistor may also be used. In this case, the base shown in the embodiment is the gate, the emitter is the source, and the collector is the drain.

  In the above description, the balun 113, the despreading unit 114, and the quadrature demodulation unit 116 are integrated and formed on the same semiconductor substrate. In contrast, the capacitors 118a and 118b, the buffer amplifiers 119a and 119b, and the differential amplifier 210 may be integrated and formed on the same semiconductor substrate.

  In the embodiment, the received signal is converted into a balanced signal. However, the received signal may be processed as an unbalanced signal. In this case, the number of transistors used can be reduced.

  The present invention can be realized as a spread spectrum radar receiver capable of realizing a precise radar spectrum in which the chip size can be reduced and the power consumption can be reduced and the peak intensity of the received signal can be stabilized. Can be used as a radar device.

It is a block diagram of the receiving part of the conventional spread spectrum radar receiver. It is a circuit block diagram of the conventional despreading part and orthogonal demodulation part. It is a simplified diagram showing the operation of a conventional despreading unit and orthogonal demodulation unit. 1 is a configuration block diagram of a spread spectrum radar receiver according to Embodiment 1. FIG. 2 is a configuration diagram of a receiving unit according to Embodiment 1. FIG. It is a circuit block diagram of a balun. FIG. 3 is a circuit configuration diagram of a despreading unit and an orthogonal demodulation unit according to the first embodiment. 6 is a simplified diagram illustrating operations of a despreading unit and an orthogonal demodulation unit according to Embodiment 1. FIG. 6 is a circuit configuration diagram of a receiving unit included in a spread spectrum radar receiver according to Embodiment 2. FIG. It is a circuit block diagram of a differential amplifier.

Explanation of symbols

100 spread spectrum radar receiver 110, 110a, 300 receiving unit 111, 301 receiving antenna 112, 302 low noise amplifier 113, 330 balun 114, 303 despreading unit 115, 304 phase shifter 116, 305 quadrature demodulating unit 116a, 116b, 305a, 305b Balanced modulator 117, 306 Local oscillator 118a, 118b, 165 Capacitor 119a, 119b, 307a, 307b Buffer amplifier 120, 310 Reception PN code generation unit 130, 320 Signal processing unit 140 Control unit 150 Spread spectrum type Radar transmitters 161, 162, 163, 164 Transmission lines 201, 211, 331 Current power supply circuit 210 Differential amplifier

Claims (11)

A spread spectrum radar receiver for receiving a spread spectrum spread signal,
A signal receiver for receiving the spread signal as a received signal;
By despreading the received signal received by the signal receiver using a pseudo-noise code, a current having the same current value as the current value of the first despread signal and the line through which the first despread signal propagates A despreading unit that outputs a second despread signal propagating through the line through which the
A quadrature demodulator that outputs the in-phase signal and the quadrature signal by performing quadrature demodulation on the first despread signal and the second despread signal;
The despreading unit includes a first transistor pair including a first transistor and a second transistor having the same characteristics,
The first transistor and the second transistor receive the received signal and despread the received signal by turning on or off according to the pseudo-noise code, and the first transistor despreads the first despread signal. And the second transistor outputs the second despread signal,
The orthogonal demodulator
A first demodulator that demodulates the first despread signal using a first local oscillation signal and outputs the in-phase signal;
A second demodulator that demodulates the second despread signal using a second local oscillation signal whose phase of the first local oscillation signal is shifted by 90 degrees and outputs the quadrature signal. Spreading radar receiver. The spread spectrum radar receiver according to claim 1, wherein the first transistor and the second transistor have a base or a gate connected in common and an emitter or a source connected in common. apparatus. The signal reception unit converts the received spread signal into a balanced reception signal composed of a positive reception signal and a negative reception signal,
The first despread signal is a balanced signal composed of a first positive despread signal and a first negative despread signal;
The second despread signal is a balanced signal composed of a second positive despread signal and a second negative despread signal;
The despreading unit further includes a second transistor pair having the same configuration as the first transistor pair,
The first transistor pair receives the normal reception signal, and despreads the normal reception signal by turning on or off according to the pseudo noise code, and the first normal / despread signal and the second normal / reverse signal Outputs a spread signal,
The second transistor pair receives the negative reception signal and despreads the negative reception signal by turning on or off according to the pseudo noise code, and the first negative despread signal and the second negative inverse signal The spread spectrum radar receiver according to claim 1, wherein a spread signal is output. The pseudo-noise code is a balanced pseudo-noise code composed of a positive pseudo-noise code and a negative pseudo-noise code,
The despreading unit further includes a third transistor pair and a fourth transistor pair having the same configuration as the first transistor pair,
The first transistor pair despreads the normal reception signal by turning on or off according to the positive pseudo-noise code, and outputs the first normal despread signal and the second normal despread signal,
The second transistor pair despreads the negative reception signal by turning on or off according to the positive pseudo-noise code, and outputs the first negative despread signal and the second negative despread signal,
The third transistor pair receives the positive reception signal, and despreads the positive reception signal by turning on or off according to the negative pseudo-noise code, and the first negative despread signal and the second negative diffusion signal Output despread signal,
The fourth transistor pair receives the negative reception signal, and despreads the negative reception signal by turning on or off according to the negative pseudo-noise code, and the first positive / despread signal and the second positive diffusion signal. The spread spectrum radar receiver according to claim 3, wherein a despread signal is output. The spread spectrum radar receiver further comprises:
A code generator for generating the pseudo-noise code;
The spread spectrum radar receiver according to claim 3, further comprising: an amplification circuit that amplifies the pseudo noise code and outputs the amplified pseudo noise code to the despreading unit. The signal receiver is
Including a balun circuit that converts the received spread signal into the balanced received signal and outputs it to the despreading unit;
The spread spectrum radar receiver according to claim 3 or 4, wherein the balun circuit is composed of passive elements. The balun circuit is
A first transmission line in which the spread signal which is an unbalanced signal is input to one end and the other end is grounded;
Including a second transmission line and a third transmission line electromagnetically connected to the first transmission line;
One end of the second transmission line and one end of the third transmission line are grounded, and from the other end of the second transmission line and the other end of the third transmission line facing each other, the positive reception signal and the 7. The spread spectrum radar receiver according to claim 6, wherein a negative received signal is output. The spread spectrum radar receiver further comprises:
A first capacitor connected in parallel to the output line of the first demodulator to remove high frequency components of the in-phase signal;
The spread spectrum type according to any one of claims 1 to 7, further comprising: a second capacitor connected in parallel to the output line of the second demodulator and removing a high frequency component of the orthogonal signal. Radar receiver. The despreading unit and the quadrature demodulating unit are integrated circuits having a common current source, and are formed on the same semiconductor substrate. 2. A spread spectrum radar receiver according to item 1. The spread spectrum radar receiver according to any one of claims 1 to 9, wherein the transistor is a hetero-bipolar transistor. A semiconductor device used in a spread spectrum radar receiver that receives a spread spectrum spread signal,
A signal receiver for receiving the spread signal as a received signal;
By despreading the received signal received by the signal receiver using a pseudo-noise code, a current having the same current value as the current value of the first despread signal and the line through which the first despread signal propagates A despreading unit that outputs a second despread signal propagating through the line through which the
A quadrature demodulator that outputs the in-phase signal and the quadrature signal by performing quadrature demodulation on the first despread signal and the second despread signal;
The despreading unit includes a transistor pair including a first transistor and a second transistor having the same characteristics,
The first transistor and the second transistor receive the received signal and despread the received signal by turning on or off according to the pseudo-noise code, and the first transistor despreads the first despread signal. And the second transistor outputs the second despread signal,
The orthogonal demodulator
A first demodulator that demodulates the first despread signal using a first local oscillation signal and outputs the in-phase signal;
A second demodulator that demodulates the second despread signal using a second local oscillation signal whose phase is shifted by 90 degrees and outputs the quadrature signal. apparatus.

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